1. Field of the Invention
This application relates to waste treatment tank covers. More particularly, the application relates to a cover for a launder channel with panel members.
2. Description of Related Art
In the field of wastewater treatment, clarifier tanks are used to separate solids from the water. Clarifier tanks typically receive influent water through a pipe located at or near the bottom of the tank, that then carries the water up through the center of the tank and discharges the water near the top of the tank. The solids in the influent water settle to the bottom of the tank with the clean water forced under a scum baffle, over a weir and into a launder channel mounted around the periphery of the tank.
A common problem in clarifier tanks is the buildup of algae and other contaminants on the surfaces of the scum baffle, the weir and the launder channel. Not only is the algae growth unsightly, it can affect the hydraulic performance of the clarifier, clog downstream filters, cause problems with UV (ultra-violet) disinfection equipment and generally become an expensive maintenance issue.
To correct this, in the prior art a cover is placed over the launder channel, the scum baffle and the weir to block sunlight from reaching these surfaces, thereby inhibiting the growth of the algae.
Prior art FIG. 1 shows an exemplary cover over a launder channel. Typically, these covers are comprised of numerous consecutive panel members installed over the launder channel around the entire circumference of the tank.
Prior art FIG. 2 shows a top view of a standard arrangement of three consecutive panels covering a portion of the launder channel of a clarifier tank. A common feature of these covers is a tab or extension added to the ends of certain panels that serve to cover the seam between individual panels to ensure that no light reaches the surfaces below.
One typical prior art cover arrangement has consecutive cover panel sections, where alternating panels have tabs to seal out sunlight. While they are effective, these tabs require that the cover panels roust be opened in a specific sequence in order that all of the panels can be opened.
For example, in prior art FIG. 3 a first “A” panel has tabs on either side of the panel. The adjacent cover panels are referred to as “B” panels and have no tabs, but may have stiffening flanges along the curved edges of the panel to keep the panel from sagging under the weight of the A panel that rests on the B panel. In this arrangement, the tabs on the A panel overlap the edges of the B panel to seal out the light.
A typical cover arrangement using “A” and “B” type panels is shown in prior art FIG. 4, with an A panel on either side of a B panel. To open the center B panel, it is first necessary to open the A panels on either side. This is sometimes referred to as an “A-B-A” cover (arrangement).
An alternative cover is shown in prior art FIG. 5. Here, each panel has an “A”-type tab at one end and a stiffening flange at the other.
The A end of the panel rests on the B end (stiffening flange only) of the adjacent panel. This allows the cover to be opened in only one direction. To open the cover, the operator stands in one place, for example, the bridge of the clarifier, opens one cover panel, enters the launder and proceeds to open the cover panel by panel going in one direction and then reversing himself to close the cover. This is often referred to as an “A-B Zipper” arrangement.
These prior art A-B-A and A-B Zipper arrangements are common whether the cover is mounted to the tank wall and the panels open back toward the outside of the clarifier, or when the cover is mounted to the weir wall of the clarifier and opens toward the center of the clarifier.
These prior art designs work well when the clarifier is located at ground level and plant personnel have ready and convenient access to the clarifier launder. However, a large number of clarifiers are elevated, or otherwise built in a configuration where access to the launder is neither safe nor convenient. Often, it is necessary to reach a specific cover panel to perform maintenance or find the source of a problem. There is a substantial effort involved in locating a particular area on the circumference of a two hundred foot diameter tank standing fifteen feet in the air, while maneuvering large ladders into position against the tank wall and opening three or snore cover panels to investigate a problem. Similarly, maintenance personnel may be required to open half the covers in a zipper cover arrangement, walking in the launder itself, to reach a trouble spot.